Re: [PATCH v2 1/2] iio: adc: ti-ads7950: Allow to use on ACPI platforms

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Tue, 2017-08-01 at 11:21 -0500, David Lechner wrote:
> On 08/01/2017 10:45 AM, Andy Shevchenko wrote:
> >    
> > > > > +	/* Use hard coded value for reference voltage in ACPI
> > > > > case */
> > > > > +	if (ACPI_COMPANION(&spi->dev))
> > > > > +		st->vref_mv = TI_ADS7950_VA_MV_ACPI_DEFAULT;
> > > > 
> > > > Instead of checking or ACPI, you could just say "if we have a
> > > > dummy
> > > > regulator, then use the default value".
> > 
> > 
> > > Agreed. Sounds sensible to me.  Hopefully in DT people will
> > > provide the right regulator, but chances are this won't
> > > always happen.
> > 
> > There is no call like
> > regulator_is_dummy()
> > (and, looking into the code of regulator framework, can't be)
> > 
> > Can you elaborate a bit, maybe I'm missing something obvious?
> > 
> 
> I haven't tested this, but shouldn't regulator_get_voltage() return
> an 
> error for a dummy regulator? You could use this as your test.

While it would work it's very fragile.

_regulator_get_voltage() will return error code even for normal
regulators if something happened there. And user gets an impression that
everything is okay while it's not. 

So, I wouldn't go this way.

> 
> static int ti_ads7950_get_range(struct ti_ads7950_state *st)
> {
> 	int vref;
> 
> 	vref = regulator_get_voltage(st->reg);
> 	if (vref < 0)
> -		return vref;
> +		vref = 2500000;
> 
> 	vref /= 1000;
> 
> 	if (st->settings & TI_ADS7950_CR_RANGE_5V)
> 		vref *= 2;
> 
> 	return vref;
> }
> 

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy